[racket] Low level manipulation on numbers
Dear all, I am trying to write a small implementation of Protocol Buffers ( http://code.google.com/p/protobuf/ ) and I have difficulties with bit manipulations, especially to transform a negative integer into a series of bytes and back. I can not find an implementation of a non-arithmetic shift for fixnums, and a way to specify which size of fixnum to construct. I can't also find an easy way to get the byte representation of flonums. Do you have any idea? Best regards, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] Low level manipulation on numbers
Thank you so much for your very quick answer. It seems that the conversion to and from bytes are what I was looking for. With that, it is quite easy to do all the manipulations I want. Best, Nicolas. On Sat, Oct 8, 2011 at 6:57 PM, Matthew Flatt wrote: > At Sat, 8 Oct 2011 17:41:35 +0100, "nicolas.o...@gmail.com" wrote: > > I am trying to write a small implementation of Protocol Buffers ( > > http://code.google.com/p/protobuf/ ) and I have difficulties > > with bit manipulations, especially to transform a negative integer into a > > series of bytes and back. > > > > I can not find an implementation of a non-arithmetic shift for fixnums, > and > > a way to specify which size of fixnum to construct. > > There aren't different sizes of fixnums. When you want to convert an > exact integer to bytes, then `integer->integer-bytes' lets you specify > the size. > > There also isn't a logical shift operator, if I understand what you're > after. If you work with positive integers, then `arithmetic-shift' > (plus `bitwise-and'?) behaves like a logical shift. If you want > logical-shift effects for finite 2's complement representations, then > you probably don't really want to work on fixnum representations, which > are 63 or 31 bits, but instead some power of 2 via bitwise operations > like `bitwise-ior', `bitwise-and', and arithmetic shifts of negative > numbers. Note also that `integer-bytes->integer' lets you say whether > to interpret a set of bytes as unsigned or as 2's complement. > > > I can't also find an easy way to get the byte representation of flonums. > > `real->floating-point-bytes' > > -- Sent from an IBM Model M, 15 August 1989. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
[racket] begin and let/cc
Dear all, I don't understand this behaviour: > (define k #f) > (begin (let/cc out (set! k out)) 5) 5 > (k #f) #f > (let () (let/cc out (set! k out)) 5) 5 > (k #f) 5 Does begin something special regarding continuation? Best regards, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] begin and let/cc
Thank you so much. That clarifies it. Is there a list of forms that splice into their context? On Fri, Oct 14, 2011 at 9:27 PM, Jos Koot wrote: > ** > In addition to my previous mail:put the code in the definitions window of > DrRacket and use the macro stepper to see how the code is expanded. > Jos > > -- > *From:* users-boun...@racket-lang.org [mailto: > users-boun...@racket-lang.org] *On Behalf Of *nicolas.o...@gmail.com > *Sent:* viernes, 14 de octubre de 2011 21:40 > *To:* users@racket-lang.org > *Subject:* [racket] begin and let/cc > > Dear all, > > I don't understand this behaviour: > > > (define k #f) > > (begin (let/cc out (set! k out)) 5) > 5 > > (k #f) > #f > > (let () (let/cc out (set! k out)) 5) > 5 > > (k #f) > 5 > > > Does begin something special regarding continuation? > > > Best regards, > > Nicolas. > -- Sent from an IBM Model M, 15 August 1989. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
[racket] Liveliness of variables and GC
Dear all, I am struggling to find the origin of a memory leak in a small program I wrote. In order to help me searching, I would like to know a few details on the implementation of Racket. 1) (define (f x y) (lambda () x)) (define g (f 2 veryBigObject) ) Can I be sure that g does not retain a pointer to veryBigObject? 2) (g is a function) (define (f) (let ([x veryBigObject]) (g))) Can I be sure that veryBigObject is not retained by f during the execution of g? 3) Same program. g now captures its continuation. Can I be sure that this continuation does not retain veryBigObject? Best regards, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] Liveliness of variables and GC
Thank you so much for the very quick answer. Best, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] Liveliness of variables and GC
I am still struggling a bit. Is there a way to profile/snapshot/inspect memory? What is the canonical way to find a memory leak in a Racket program? Best regards, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
[racket] Memory and delimited continuations
Dear all, Following on my memory leak problem, I managed to minimise my program. And I still don't understand why it leaks. Here is a minimised example: (define prompt1 (make-continuation-prompt-tag 'p1)) (define prompt2 (make-continuation-prompt-tag 'p2)) (define (capture-and-abort prompt-tag) (call-with-composable-continuation (lambda (k) (abort-current-continuation prompt-tag k)) prompt-tag)) (define (test i) (call-with-continuation-prompt (lambda () (call-with-continuation-prompt (lambda() (for ((j i)) (capture-and-abort prompt1) (capture-and-abort prompt2))) prompt2)) prompt1)) (test 10) Calling test with any number 100 000 or higher will allocate memory very fast. What is the reason for that and how can I solve this? Best regards, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] Memory and delimited continuations
Thank you very much. If I can help in any way, please ask. Best regards, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] Memory and delimited continuations
The new master version got rid of my memory leak. Thank you so much for the quick patch. Best, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] DrRacket needs work
I like Dr Racket very much, but I have a small problem that might be easy to solve: When hitting return in the middle of a line, in the REPL, in does not evaluate the line but adds a line break. I think this might be the right behaviour but I would like to have a way to send the s-expr to evaluation without having to go to the end of the s-expr first. Is there a way to do that? Best, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] DrRacket needs work
It works. Thank you very much. On Sun, Nov 13, 2011 at 1:40 PM, Chris wrote: > +1 on this. I know other REPLs (at least python) do the same, but I think > behaving like a command line would be more natural to most people. > Ctrl+Enter to evaluate, Enter to line break would be nice too. > > _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
[racket] Sending a method as a symbol
Dear all, Is there a function to send to a class with a dynamic symbol instead of a static one? As in (send 'method-name) send seems to reduce to find-method/who, but this function is not exported. Best regards, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] Sending a method as a symbol
On Tue, Nov 15, 2011 at 8:14 PM, Grant Rettke wrote: > > That is like eval but for talking to objects? > More like looking up an interned symbol from a namespace. (A very limited form of eval...) Best, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] Implementing delimited continuations using a CPS transform
I think your solution is perfectly sensible. shift/reset needs two CPS transformations. Then you have two continuations : one local (up to the next reset), one global (from the next reset to the toplevel). The global one is usually called the meta-continuation, and often denoted m. I think this is explained in "Abstracting Control" by Filinski and Danvy. This blog post shows an evaluator for shift/reset where you can see the two continuations at work: http://calculist.blogspot.com/2006/11/shift-and-reset-via-two-continuations.html Best regards, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] Implementing delimited continuations using a CPS transform
> But you could also break the tail-call discipline of CPS and translate [shift > e] as \k. (k [e](\x.x)) > Or you can use our 'abstract' continuations to manipulate a stack of > continuations directly. What are your 'abstract' continuations? Sounds very interesting. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] Implementing delimited continuations using a CPS transform
It is often used to represent a function that applies on a term, or an expression. [ t ] means the function [] applied to t. In those papers, it often represent a CPS transform. Like [ x ] = \ k . k x would mean "the cps transform of 'x' is '\ k . k x' , or cps(x) = \ k . k x. Using [ _ ] is a bit nicer. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
Re: [racket] Racket Web Server
> > PS You also mentioned sedna. I'm guessing you might also be frustrated > with relation databases? I am also tired of writing ORMs and am using the > move to Racket as a good chance to move to different ways of storing > data, I've found that Riak http://wiki.basho.com/ works well, and its the > best fit for the type of apps I develop. Hi, Riak looks very nice indeed. Do you have any library to interface Racket with Riak? Best regards, Nicolas. _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
